The present invention relates to an antenna system and more particularly to a system that provides convertibility, that is to say, that enables the initial installation of a conventional or NTSC antenna which is "field convertible" into two separate antennas to allow for HDTV transmission at some future date.
Many years have elapsed since the concept of high definition television (HDTV) was first introduced. The well-known advantage to this form of television is that significantly improved picture quality and sound are expected. However, there has been a great reluctance on the part of broadcasters to take any initiatives in bringing high definition television into common use, chiefly for the reason that the government (FCC) must first approve the transmission standards. Further, they are in the dark as to what channels may be assigned to,them for high definition television broadcasting.
Accordingly, generally stated, within the broadcast community the problems concerning how to build and where to install a new HDTV broadcast antenna have necessarily been deferred. However, solutions to the aforementioned problems must be reached. In other words, that "bridge" must be crossed now.
The present invention recognizes that structural and picture quality requirements for broadcasting point to one solution. Such solution requires a low gain antenna for the transmission of the HDTV signals, whereby the lower gain (and hence shorter length) HDTV antenna and the conventional or NTSC antenna can be integrated into one unit for direct replacement on existing towers with little or no reinforcement required for the towers.
It has been found that if this solution of a relatively low-gain HDTV antenna integrated with a conventional antenna is not adopted, the alternative approaches will involve mechanically impractical and--from a picture quality standpoint--undesirable solutions, involving very large increases in tower loading for such stack configurations. In other words, a new tower would be required to handle the greater loading.